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UNIT 2 BIOLOGICAL OF *

Structure 2.1 Objectives 2.2 Introduction 2.3 Theories of Evolution 2.3.1 Pre-Darwin Theories of Evolution 2.3.2 Darwinism 2.3.3 Synthetic Theory of Evolution 2.4 Hominization 2.4.1 2.4.2 Encephalization 2.4.3 Sexual Dimorphism 2.4.4 Other Factors 2.5 Evolution 2.5.1 Before Homo 2.5.2 Evolution of Genus Homo 2.6 Summary 2.7 Key Words 2.8 Answers to Check Your Progress Exercises 2.9 Suggested Readings 2.10 Instructional Video Recommendations

2.1 OBJECTIVES This Unit deals with the biological evolution of humans. After going through the Unit, you will be able to: z Describe the phenomenon of evolution; z Compare and evaluate the various theories of evolution; z Explain the contribution of Darwin to evolution; z Appreciate how fossils are the greatest evidence of evolution of humans; z Identify differences between apes and humans; and z Explain how apes transformed to Homo sapiens.

2.2 INTRODUCTION Hall and Hallgrímsson (2008) defined evolution as ‘change in the heritable characteristics of biological populations over successive generations’. Herbert Spencer, an English philosopher and sociologist, first articulated the term ‘evolution’ in 1862 to denote the

* Prof. Rashmi Sinha, Faculty of Anthropology, School of Social Sciences, Indira Gandhi National 32 Open University, New Delhi. historical development of life. Evolution is the progressive change within the organism. Biological This change is termed as ‘micro-evolution’when it occurs over a period of time and Evolution of referred as ‘macro-evolution’ when it involves the transformational changes from one Humans being to the other. Charles Darwin, a significant evolutionist defined evolution as ‘descent with modification’which implies that closely related species resembleeach other because of the inheritance; and differ from each other owing to the hereditary differences acquired during the separation of their ancestors. Before embarking on the evolution of human beings, let us first understand the process of evolution, with its various theories.

2.3 THEORIES OF EVOLUTION The evolutionary thought ranges from classical theories of Aristotle to the modern synthetic theory of evolution. These various theories serve as basis of understanding the evolution of life and its diversity. These also determine the successive stages unto which the modern theory of evolution came into being. 2.3.1 Pre-Darwin Theories of Evolution Charles Darwin is known to be the scientist who changed the course of evolutionary theory and established a firm ground on which evolution could be studied. However, before Darwin, many theories were put forward which actually laid down the path for the growth of evolutionary thought. Beginning from Greek thinkers to the theories of Lyell, the Pre-Darwin theories talk about ways in which scholars before Darwin understood evolution. Greek Greek philosophers such as Aristotle (384-322 BCE), Herodotus (484-425 BCE) and Empedocles (504-433 BCE) were the pioneer scholarswho proposed the idea of evolution. They believed in the idea of the continuity of life forms giving rise to new forms. Aristotle proposed that living organisms have certain inner abilities to strive better through the process of adaptation. He observed this potential among plants, animals and humans. Being the first to highlight the insights of humans, Aristotle is also credited for coining the term Anthropology or the study of human beings (for further details see Section 1.8, Unit 1 of this course) and is therefore known as the ‘Father of Anthropology’. Herodotus and Empedocles also developed certain ideas related to living beings and their biological evolution. The ideas of these philosophers indicated the concept of adaptation; plants evolving before animals indicating the gradual evolution of higher organisms, and finally the humans. The obsolete Theory of Spontaneous Generation or Abiogenesis holds that life originated from inanimate and inorganic matter such as manure, dew, rotten slime, dry wood, sweat and meat etc. Until the 17th century, scientists like Aristotle, Thales, Plato and Von Helmont supported the idea of abiogenesis. By the middle of the 19th century abiogenesis was refuted by Francesco Redi, Spallanzani and Louis Pasteur. Theories of Medieval Times The medieval times also famous as ‘the Christian era’ in the European world refuted the views of evolution given by Greeks. This time period was dominated by the Christian Theory of Special Creation. According to this theory all living organisms present on the earth were created by supernatural power in six days. Since all these living forms 33 Evolution of are created by divine power, they are non-changeable and permanent from the day of Humankind their creation. Spanish Priest, Father Suarez (1548-1671) was a strong supporter of this theory which was followed until middle of the 19th century. The Theory of Eternity of Present Condition proposes the unchanging nature of the universe. This theory states that organisms remain unchanged throughout their individual existence and will remain in the same form throughout eternity. Theories of Organic Evolution By mid-18th century the idea of the biological evolution of living organisms had revolutionized the scientific world. During this time Carl Linnaeus (1707-1778) a Swedish Botanist, published his immortal work ‘Systema Naturae’(1735). Linnaeus also introduced the binary nomenclature of living organisms and designated each organism with two Latin names, one for Genus and the other for Species. Since the time of Linnaeus, Humans have been scientifically termed as Homo-Sapien. In the late 18th century, the French scientist, Comte de Buffon (1707-1788) who was contemporary of Carl Linnaeus, stated that life forms are not fixed and permanent. He argued that the evolution of living organisms is strongly influenced by the environment. Thereafter, another 18th century evolutionist, Erasmus Darwin (1731-1802), the grandfather of Charles Darwin, highlighted the evolutionary aspects of animals through his work and strongly recommended that the life on the earth must have been evolving for millions of years whereas the evolution of humankind is the most recent. Lamarck (1744-1829), a French naturalist, was the first evolutionary scientist who confidently proffered the idea of biological change in the living organisms. His theory of evolution explaining the origin of new species is called ‘Inheritance of Acquired Characters’. Lamarck, who possessed specialization in animal classification, perceived that the various species could be arranged into an orderly relationship that will form a continuous succession extending from the simplest little polyp to complex human. He was the first naturalist who believed that animals modify themselves in order to adapt to the altered conditions of environment. In his theory he stated that species were not constant but were derived from pre-existing species. He further suggested that the structure of an organism is majorly dependent on its function. He presented the example of Giraffe for the justification of his theory, explaining that the long-neck of Giraffe could have been evolved because of its continuous stretching and use in order to reach higher foliage on trees. Based on this observation, he propounded a theory based on four principles, namely: 1) Use and disuse of organs 2) The acquired characteristics are inherited 3) Internal urge 4) Direct environment and new desires For him, Giraffe’s long neck was an acquired character which was inherited by the next generations. Similarly, snake’s smooth body was the result of disuse of its limbs as it chose to live in burrows. Unfortunately, Lamarck’s theory of inheritance of acquired characteristics did not prove tenable among the scientific community because it was not supported by enough evidence to resolve all the queries. However, it was proved to be an important milestone in evolutionary biology. 34 George Cuvier (1769-1832) another French scientist disapproved Lamarck’s theory Biological of evolution; however, he supported views on fossil evidence and biological relationship. Evolution of He believed that dinosaurs disappeared from the planet due to ‘fixity’ of species. He Humans further advocated the theory of ‘Catastrophism’ which argues that changes in the earth’s crust have been caused by sudden natural disasters.The theory however was not fully supported by scientific explanation. Charles Lyell (1797-1875), a significant geologist and English lawyer, refuted Cuvier’s Catastrophism theory. Lyell in his famous book ‘Principles of Geology’ (1830-1833) which was published in three-volumes, reported that unlike the Biblical view, the earth must be older than few thousand years; and it has undergone numerous structural and climatic changes that occurred gradually over geological time scale through natural processes like, erosions, earthquakes, glacial movements and volcanoes. He also presented conclusive evidence for the theory of uniformitarianism which holds that the earth’s natural changes acted in the same manner and intensity in the past as they act in the present. 2.3.2 Darwinism A study of existing theories before Darwin, led Charles Darwin (1809-1882) to think of the process of evolution of living beings and subsequently, in 1859, he propounded his famous theory of natural selection in his famous book ‘Origin of Species’. According to Darwin, natural selection is the process by which organisms adapt to changes in their environment and are able to survive and thus reproduce. Darwin was influenced by the works of significant scholars such as Sir Charles Lyell, T.R. Malthus and Alfred Russel Wallace. The Two Major Influences on Darwin

Malthus and his Theory of Population Alfred Russel Wallace and his Principle of Natural Selection z Thomas Robert Malthus (1766-1834) was an 18th century English philosopher and z Alfred Russel Wallace (1823-1913) was a economist. British naturalist, biogeographer, author z Malthus proposed the principle that while and humanitarian. human populations grow exponentially z Wallace was a co-discoverer of the theory (i.e., double with each cycle), food of evolution with Darwin. production grows at an arithmetic rate (i.e. uniform increase in each interval of time). z The working principle of Wallace’s theory, like that of Darwin, was based on the z The theory was aimed to highlight that natural selection and adaptation of the growth in population will lead to a species to their environment. shortage of food production and food availability. z Wallace and Darwin’s research papers were com-bined and published under the z This theory was published in 1798 under joint authorship in 1859. the title ‘An Essay on the Principle of Population’ which was modified and published again by Malthus in the next edition of 1803.

Darwinism consists of five principles which are: i) Over-production or prodigality (lavishness) of over-production: Influenced by the Malthusian theory of population, this concept is related to reproduction and lays down that more individuals are born in each generation than will be able to survive. 35 Evolution of ii) Variation and Heredity: Individuals of the same species are not all alike and Humankind differ from each other in various characteristics due to natural variations. Favourable adaptations are inherited and are passed on to the off springs of the next generations. iii) Struggle for existence: Organic individuals tend to increase in a geometrical ratio, whereas food production only increases in an arithmetic ratio. As a result, there is a struggle for the limited resources. Only selected individual get access to the limited resources and rest get eliminated in this struggle for existence. iv) Survival of the fittest or natural selection: Individuals with favorable characteristics or variations have a better chance of surviving and reproducing than those who lack these characteristics. v) Modifications of species: With gradual change in the environment that occurs over long periods of geological time, genes for selection also change. As a result of these additive changes species gets modified and becomes totally different from its ancestral population. Darwinism became the most influential theory of evolution, but it was unable to define how natural selection actually leads to evolution. Darwin’s idea was however taken forward by a set of scholars like Charles Lyell,Thomas Huxley, Earnest Heckle, August Weismann, Alfred Russel Wallace and George Simpson. These scholars are known as Neo-Darwinists as they supported Darwin’s concept of natural selection. Later, some scholars of this school such as Sewall Wright, Ronald Fisher, and J.B.S. Haldane described natural selection by explaining modern synthesis, or Neo-Darwinism. 2.3.3 Synthetic Theory of Evolution This theory of evolution was essentially a combination of natural selection, genetic inheritance, population genetics, systematics and theories of speciation and macroevolution. In addition to it, this theory also emphasizes non-selectionist factors of evolution, especially isolation, mutations, and recombination (Reif et al., 2000). Isolation of living individuals into various small groups or populations under geographical or physical barriers is one of the important factors responsible for evolution. These barriers include oceans, rivers and mountains that prevent the process of interbreeding between related individuals. On the other hand, mutations which are responsible for the alterations in the structure of a gene produce variations in the individuals. These variations can be harmful or lethal or recessive to the normal genes. Most geneticists believed that the frequency of gene alterations by mutation was much smaller than the change by natural selection. With a more complete understanding of mechanism of inheritance, it is now understood that the evolution is actually the total aggregate of the genetically inherited changes in the individuals who are the members of the gene pool of a population and the factors of evolution function on the whole population rather than the individuals alone. The following three aspects highlight the differences between Darwinism and modern theory of the mechanism of evolution: i) Apart from the natural selection the modern theory identifies several significant forces of evolution such as mutation, isolation and genetic drift. ii) The modern theory of evolution recognizes the discrete inherited entities in a human that are known as genes. The multiple forms (alleles) of a gene are responsible for variation within a population. 36 iii) This theory further suggests that new species are generally formed due to the Biological gradual accumulation and inheritance of small genetic changes. Evolution of Humans Basically, the modern synthetic theory explains the functioning of evolution at the level of genes, phenotypes and populations. This theory is however often challenged by Neo-Mutationism. Driven by molecular biologist Masatoshi Nei along with many others, the theory of Neo-mutationism advocates the phenomenon of mutation, rather than natural selection, as the central force of evolution. These theories of evolution have been responsible for making history of understandable. Evidence from the past, in the form of fossils played a key role in determining how humans evolved from apes. The principles of evolution were applied to the evidence excavated by paleoanthropologists and archaeologists. The evidences in the form of hominid fossils were able to provide a trajectory to human evolution. It determined how ape-like mammals evolved into modern human beings. Scientists suggest that this process took about 6 million years. Check Your Progress Exercise-1 1) Define evolution in 50 words...... 2) What are the main features of Lamarck’s theory of evolution? ...... 3) List down the main features of Darwinism...... 4) Fill in the blanks: a) According to Malthusian theory of Population, human population grows ...... while food production grows at an ...... b) The theory of ‘Inheritance of Acquired Characters’ was proposed by ...... c) Alfred Russel Wallace proposed the principle of ...... 37 Evolution of 5) How is Darwinism different from the synthetic theory of evolution? Humankind ...... 2.4 HOMINIZATION Homonization is defined as the gradual emergence of anatomically modern humans from their primate ancestors of genus Homo. The Swedish naturalist (student of natural history) Carl Linnaeus was the first one to use the Latin word ‘homo’, which stands for human being. Homo is the genus that comprises the species Homo sapiens, which includes modern humans, as well as several extinct species which are closely related to modern humans, most notably . The story of human evolution began with primates, 65 million years ago. Beginning from prosimians to monkeys, apes, great apes and finally humans. It was Darwin who made it possible to understand a link between apes and humans. In his ‘Origin of Species’ he put forth the idea of evolution of new species from their forerunners. The history of human evolution also involves a breakthrough stage between the hominids and the humans. This stage marks the beginning or birth of human beings, separated from its ancestor, apes.

Figure 2.1 : Primate tree Credit: Wikimedia Commons Source: https://en.wikipedia.org/wiki/File:PrimateTree2.jpg The most closely linked ancestors of humans are said to exist during the late Miocene Epoch (23 million to 5.3 million years ago). Due to evergreen broad-leaved forests turning into open woodlands, shrub-lands, grasslands, and mosaic habitats, sometimes with denser-canopied forests bordering lakes, rivers, and streams, ape-like primates flourished in this epoch. Such diverse environments stimulated novel adaptations involving locomotion in many types of animals, including primates. This led to a shift from arboreal 38 to terrestrial life. The development of bipedalism i.e. the ability to walk upright enabled hominins to strive better in the open woodlands. We will discuss below the major Biological distinguishing features between an Ape and a human, of which Bipedalism was the most Evolution of distinguishing. Humans

Figure 2.2 : Hominization Credit: Prof. Pedro Flores, Professor de Geografia e Historia en IES Blas de Otero Source: https://www.slideshare.net/pflores88/the-prehistory-72472639 2.4.1 Bipedalism Bipedalism is a major reason behind the skeletal changes shared by all bipedal hominids. or are the most primitive examples of bipedalism. These are regarded as the last primates, sharing ancestry with knuckle walkers — gorilla and chimpanzee. Bipedalism had several advantages such as: 1) Upright walking freed the hands for reaching and carrying food, 2) Bipedalism saved energy during locomotion, 3) It enabled long distance running and hunting, 4) It provided an enhanced field of vision, 5) It assisted in avoiding hyperthermia by reducing the surface area which was exposed to direct sun, 6) It helped in multi-tasking and increased productivity, and 7) Bipedalism led to a fairly proportionate ratio of hindlimbs and forelimbs, opposite to long fore or hindlimb apes. Opposable thumb helped in tool making. Other changes associated with bipedalism include long toe, shortening of the pelvis and birth canal and other skeletal changes. 2.4.2 Encephalization Another significant change in the process of hominization was the increase in the size of human brain which grew nearly three times bigger in size than that of a gorilla or chimpanzee. This process, of the enlargement of the brain, is termed as Encephalization and it began with . Consequently, there was an increase in temporal lobes of the brain, used in language processing and pre-frontal cortex, used in complex decision making, (evolution of humans is discussed in Section 2.5 of this Unit). 39 Evolution of 2.4.3 Sexual Dimorphism Humankind Another factor distinguishing apes from human ancestors is sexual dimorphism i.e. the condition in which the two sexes of the same specie exhibit different characteristics. There emerged a reduction in sexual dimorphism in humans which is characterized by the reduction of the male canine toothin comparison to other ape species (except gibbons, also called the smaller apes) and reduced brow ridges and general robustness of males. Another significant physiological change which was related to human sexuality was the evolution of hidden estrus (state of sexual receptivity). 2.4.4 Other Factors Several other factors such as the ulnar opposition (the contact between the thumb and tip of the little finger of the same hand), increased vision as opposed to smell, smaller gut, change in dental arcade, evolution of sweat glands etc. led to the differentiation of humans from the apes. The connection between apes and humans had been established on the basis of many evidences. Molecular biology found a 95-99% similarity of DNA between a chimpanzee and a human. The split between chimpanzee and hominin is marked at 4-8 million years ago. The most prominent evidence of human evolution came with the discovery of fossil records. Paleoanthropologists were able to ascertain evolution of humans from apes by finding similarities and differences in the fossils of apes and human beings. The fossil remains helped in defining the successive stages in the evolution of modern human beings. x The fossils discovered in 1891 were found in Trinil, in the island of Java, Indonesia. x Based on the place of its discovery, the fossil is popularly known as the ‘’. x The specie was discovered by a team of excavators headed by Eugene Dubois. x The specimen was originally thought to be a new specie between humans and apes and was classified as Pithecanthropus erectus. x Eventually in the 1940/50s, German biologist Ernst Mayr established connections between Java Man and the fossil of Sinanthropuspekinensis () whereby both were classified as being part of the same species, the Homo erectus (Detailed later in the Unit). When the first hominin fossil was found, it was mistaken to be that of a human being who might have been suffering from some kind of illness in 1891. By the 1920s when similar kind of fossils began to be discovered, these were classified as different specie.

Figure 2.3 : : A New Species on the Human Family Tree Credit: Illustration: S.V.Medaris, UW-Madison 40 Source: University of Wisconsin (https://news.wisc.edu/naledi/) Biological 2.5 HUMAN EVOLUTION Evolution of Evolution of the closest ancestors of humans can be divided into two categories: Before Humans Homo and Evolution of genus Homo (For illustration see, https://www.britannica.com/ science/human-evolution). 2.5.1 Before Homo This category is characterized by fossil evidences of hominids which had a close resemblance to humans but had a closer proximity to apes. Dryopithecus Dryopithecus is a genus of extinct ape-like animal which represents the stage of human evolution when humans and apes shared common ancestry. It was found as fossils in Miocene and Pliocene deposits (23 to 2.6 million years old) and apparently originated in Africa. Several distinct forms of Dryopithecus are known, including small, medium, and large, gorilla- sized animals. It lacks the Figure 2.4 : Fossil of Dryopithecus characteristics, Credit: Ghedoghedo, 2013 distinguishing an ape and a Source:https://upload.wikimedia.org/wikipedia/commons/0/02/ human. The canine teeth are Dryopithecus_fontani_ mio_med_francia.JPG larger than those in humans but not as strongly developed as those in other living apes. The limbs were not excessively long. The skull lacked the well-developed crests and massive brow ridges found in modern apes. So, it was a forerunner of gorillas and chimpanzees (For illustration, see https://www.thoughtco.com/dryopithecus-tree-ape- 1093073). Ramapithecus The first Ramapithecus fossil was found in 1932 in fossil deposits of Siwalik hills of North-western India. The fossil primate was dated from the Middle and Late Miocene epochs (about 16.6 million to 5.3 million years ago). Two species: Ramapithecus Punjabicus and Ramapithecus Wickeri were the first to be found. The fragments of jaw contained in the fossil encouraged an association of Ramapithecus as a distinct genus, that was the first direct ancestor of modern humans (Homo sapiens). However, when American anthropologist David Pilbeam discovered a complete Ramapithecus jaw, it had a distinctive V shape that differed markedly from the parabolic shape of the jaws of members of the human lineage. On the basis of this evidence, Pilbeam concluded Ramapithecus to have a resemblance to Sivapithecus, ancestor to orangutan (For illustration of Ramapithecus mandible discovered by Richard Leakey, see http:// www.angelfire.com/mi/dinosaurs/zramapithecus.html). Gigantopithecus A genus of large fossil ape, of which two species are known: Gigantopithecus bilaspurensis, which lived 6 to 9 million years ago in India, and Gigantopithecus 41 Evolution of blacki, which lived in China until at least 1 million years ago. These apes are known Humankind from teeth, lower jaw bones, and possibly a piece of distal humerus (bone in the upper half of the arm). They were large in size, perhaps larger than gorillas. They lived in open country and had powerful grinding and chewing teeth (For illustration, see https:// prehistoric-fauna.com/Gigantopithecus-blacki). The first specimens were found by the German-Dutch palaeontologist G.H.R. von Koenigswald in Chinese drugstores, where they were known as ‘dragon’s teeth’. The teeth, though large, have a few similarities to human teeth, and this led some palaeomorphologists to speculate that humans might have had ‘giant’ ancestors. Later discoveries of complete jaw bones demonstrated that they were from extinct apes (Rafferty, 2018). The first fossil of Australopithecus was discovered in 1924 by Raymond Dart, an anatomy professor at Johannesburg in the town of Taung in South Africa. It was the skull of a 5-year old child, with his milk teeth. The skull had many ape-like features such as a projecting face and a small brain. It also had distinctly human features for example, a rounded jaw unlike the pointed jaw of apes. The ventral position of the foramen magnum (the hole at the base of the skull from which the spinal cord emerges) suggested that the creature had walked upright. The skull was found to be 2.8 million years old and Figure 2.5 : Australopithecus fossil was named Australopithecus Credit: Durova, 2007 africanus. The skull is also popularly Source:https://upload.wikimedia.org/wikipedia/ known after the place of its discovery, commons/7/7d/Australopithecusafarensis_ as the Taung Child. reconstruction.jpg The most prominent and best preserved Australopithecus specimen is that of a female skeleton which was found in 1974 by a team of scientists led by paleoanthropologist Donald Johanson at Hadar in Ethiopia. Anthropologists assembled about 40% of her skeletons and she was nicknamed as ‘Lucy’.1 The skeleton was found to be 3.2 million years old. In 1938, another kind of fossil, in the genus of Australopithecus was found, which was named Australopithecus Robustus.

Australopithecus

The various species of Australopithecus lived during the Pliocene (5.3 to 2.6 million years ago) and Pleistocene (2.6 million to 11,700 years ago) epochs. There was Australopithecus (Au.) with species such as Au. anamensis, Au. afarensis, Au. africanus, Au. bahrelghazali, Au. garhi, and Au. sediba around 4-1.8 Million years ago. There was with species K. Platyops around 3-2.7 Million years ago. Last sub-genera were , with species P. aethiopicus, P. boisei, and P. Robustus around 3-1.2 million years ago.

1 Her name is said to have been inspired from the rock band Beatles’ famous song ‘Lucy in the 42 sky with Diamonds’. Australopithecus is differentiated from the genus Homo primarily because of smaller Biological body size, relatively smaller brain size, relatively small teeth and larger face, besides Evolution of other anatomical differences. Humans

Latest Discoveries Palaeoanthropologists are incessantly involved in the discovery of fossils. And in the recent past, many new evidences have come up regarding the origin of human being. For instance, in October 2009, Ethiopia’s middle Awash team discovered the largest record of human fossils from different species of Homo Australopithecus and . On 8th April 2010, some scientists discovered fossils of a new species of Australopithecus in South Africa . The new species, named , came from a cave called Malapa. The fossils are between 1.95 and 1.78 million years old. The fossils include a skull and partial skeleton of a young male approximately 12 to 13 years old at the time of his death, and an adult female jaw and partial skeleton. Previously, brain enlargement and the birth of larger-brained babies were considered critical factors in the origin of Homo but anew research on the fossil skeletons of Australopithecus sediba shows, that important changes in the pelvis and outer surface of the brain occurred prior to brain expansion. In December 2003, scientists mapped the genome from fragments of DNA taken from three Neanderthal fossil bones, each from different individuals, making it the first extinct species to have their DNA discovered. The fossils were recovered from Vindija Cave, Croatia, and are around 44,000 years old. In March 2015 scientists found a new fossil, named the ‘Ledi jaw’ from Ethiopia which is dated 2.75 to 2.80 million years old. The lower jaw, known only from the left half, has smaller teeth than the ancestor Australopithecus while other features bear similarities to later species of Homo, such as Homo habilis. Another breathtaking discovery took place on September 10, 2015 when fifteen skeletons were found in the Rising Star Cave in South Africa. These skeletons had feet and hands similar to that of present humans, combined with high shoulders, broad pelvis, and a flared ribcage typical of Australopithecus, the likely ancestor of Homo. Since this combination of traits is unknown in the fossil record until now, the research team gave the fossils a new species name, Homo naledi (Source: https://www.si. edu/; For more details on Homo naledi, watch https://www.youtube.com/ watch?v=oxgnlSbYLSc). Let us now move onto the Genus Homo and take note of various species which have been found around the world. 2.5.2 Evolution of Genus Homo It is believed that the first humans evolved from ancestors about 2 million years ago. Australopithecus afarensis is commonly regarded as the closest ancestor of genus Homo. Genus Homo was characterized by use of stone tools and the development of hips. Homo Habilis Homo Habilis lived from 2.8 to 1.4 million years ago. It evolved in South and East Africa in late Holocene and early Pleistocene epoch. The first fossil was discovered by a team led by Mary Leakey and Louis in 1960s from Olduvai Gorge in Tanzania, East Africa. At this site, stone tools were found along with the bones. Because of its association with tools, this early human was called Homo habilis, meaning ‘handy man’. Homo habilis 43 Evolution of was small in stature, with arms longer than legs and a skeleton much like Australopithecus. Humankind Their brains were larger and had small molars unlike Australopithecus.

Figure 2.6 : Forensic Reconstruction of Figure 2.7 : Replica of a Homo Habilis Homo Habilis skull discovered at Koobi Fora, North Credit: W. Schnaubelt & N. Kieser, 2006/ Kenya 7 Credit: Locutus Borg, 2007 Source: https://upload.wikimedia.org/ Source: https://upload.wikimedia.org/ wikipedia/commons/4/48/ wikipedia/commons/4/45/Homo_habilis- Homo_habilis.JPG KNM_ER_1813.jpg In May 2010, a new species, Homo gautengensis, was discovered in Sterkfontein Caves in Gaunteng near Johannesburg, South Africa. Two types of specimens, and Homo ergasterare placed between Homo Habilis and Homo Erectus. Homo Erectus

Homo Erectus meaning ‘upright human’ is an extinct species of genus Homo. It lived around 1.9 million years ago in Pleistocene epoch. Homo Erectus was a human of medium stature that walked upright. The braincase was low, the forehead was receded, and the nose, jaws, and palate were wide. The brain was smaller and the teeth larger than in modern humans. Homo Erectus appears to have been the first human species to control fire, some 1,000,000 years ago.

Three subspecies: Homo Erectus

Javanensis (Java), Homo Erectus Figure 2.8 : Original Fossils of Homo erectus found Pekiensis (China) and Homo in Java in 1891 Erectus Narmadensis (India) were Credit: Personal Scan 120 Source: https://commons.wikimedia.org/wiki/File: found. 44 Pithecanthropus-erectus.jpg Homo Soloensis Biological Evolution of Homo Soloensis, discovered between 1931-1933 by Gustav Heinrich Ralph von Humans Koenigswald, is a sub-species of Homo erectus. The sites whence this discovery was unearthed were along the Solo River, the Indonesian island of Java. This species is a late variant of Homo erectus and overlaps with . It also possibly overlaps with early Homo Sapiens. Morphologically it has a cranial capacity of 1,013- 1,251 cm³ (Brown, 1992) which is similar with Homo Erectus. Denisova Hominins Denisova Hominins or are extinct species or subspecies of archaic human of genus Homo. In March 2010, scientists announced the discovery of a finger bone fragment of a juvenile female who lived about 41,000 years ago, found in the Denisova Cave in the Altai Mountains in Siberia, a cave that has also been inhabited by and modern humans (Krause et al., 2010). The only physical remains discovered from this species are finger bone, two teeth and a toe bone. These evidence indicate that the Denisovans were extremely robust, perhaps similar in build to the Neanderthals. Homo Neanderthalensis The Neanderthal, often called Homo Sapien Neanderthalensis, were named after the Neander Valley of Germany where their fossils were first discovered in 1856. They lived in Europe and Asia from about 400,000 to about 28,000 years ago. The Neanderthals made diverse tools, including scrapers, spearheads and hand-axes. They lived in huts or caves, took care of their injured and sick and commonly buried their dead with objects. These burials suggests their belief in a life after death. This is the first evidence of the symbolic thinking characteristic of modern humans (Raven et al., 2005).

Figure 2.9 : Neanderthal Cranial Anatomy Credit: Jason Potter Source: https://commons.wikimedia.org/wiki/File:Neanderthal_cranial_anatomy.jpg However, there are a number of anatomical differences between modern humans and Neanderthal populations. Neanderthals had superior adaptation ability to cold, they had significantly larger brains, better vision, and were physically superior. Neanderthals went extinct around 38,000 years ago. Over recent decades two main theories have been emerged that focuses on their extinction. According to the first theory, a huge amount of stress was placed on the species due to the period of extreme cold in Western Europe. Another theory propounds that due to competition with modern 45 Evolution of humans who had bigger brains and better adaptations to the environment at the time Humankind didn’t give Neanderthals chance to sustain. During the course of evolution many traits of human intelligence, such as empathy, theory of mind, mourning, ritual, and the use of symbols and tools were developed. These traits were found to be apparent in great apes although in less sophisticated forms than found in humans, such as great ape language. Homo sapiens developed the full-fledged capability to comprehend and communicate with one another. The evolution of human cognition is closely related to the evolution of the human brain, speech and to the . Both humans and Neanderthals experienced a steady drop in the position of their hyoid bones which played a precise role in the formation of variety of rich sound. Speech also goes hand-in-hand with intelligence. Intelligence is the most cognitively advanced thing that is hard-wired into our brains. In fact, most anthropologists agree that the ‘great leap forward’, which ushered in the modern era of human existence, was due to the final cognitive advances that allowed complex language. Homo Sapiens Homo sapiens meaning ‘wise human’ is the species to which the modern human belongs. Homo sapiens have existed from the past 40,000 years ago. These are also called Cro-Magnons, named after the valley in France where their fossils were first discovered in 1868. The Cro-Magnons had a complex social organization and are thought to have had full language capabilities. They lived by hunting. They are further characterized by intra-cranial volume expansion and the elaboration of stone tool technologies, providing evidence for a transition from Homo erectus to Homo sapiens. Early Homo sapiens subsisted on hunting and gathering besides leading a sedentary life style. They lived in large caves or tent houses and involved themselves in cave paintings, engravings and other forms of art. They had a larger tool inventory and various weapons for hunting.

Figure 2.10 : Anatomical Comparison of skulls of home sapiens (left) and homo neanderthalensis (right) (In Cleveland Museum of Natural History) Credit: hairymuseummatt, KaterBegemot (https://www.flickr.com/photos/hmnh/3033749380/) Source: https://commons.wikimedia.org/wiki/File:Sapiens_neanderthal_comparison_en.png

46 Check Your Progress Exercise-2 Biological Evolution of 1) Which features characterize human beings as different from apes? Humans ...... 2) What is Bipedalism? ...... 3) What makes the genus Homo different from the rest of hominid fossils? ...... 4) Fill in the blanks: a) The best preserved Australopithecus specimen is nicknamed as ...... The fossil was discovered by paleoanthropologist ...... at ...... b) The term Homo sapiens stands for ...... c) ...... stands for the ‘Upright Human’. d) First Homo Habilis fossil was discovered by a team led by Mary Leakey and Louis in 1960s from ......

2.6 SUMMARY Evolution is a very complex phenomenon that has been studied by many scholars since the time of Greeks. Many significant theoretical contributions by Lamarck, Lyell, Mandel, Malthus led to the widely accepted theory of Darwinism. This was further polished by Fisher, Wright and Haldane who gave us the synthetic theory of evolution. These theories were characterized by a fusion of natural selection and inheritance of genes, as factors leading to evolution. These phenomena were used along with other evidence of physical anthropology to establish the origin of human being. One such evidence was fossil record, which by far has been the most reliable in ascertaining the successive stages of human evolution. Palaeoanthropologists have discovered fossils and classified them through a comparative anatomy. Apes and Humans are established as ancestors through the help of fossil records. The journey of human evolution began with primates and developed into apes. Changes in the climatic conditions led to better adaptability towards 47 Evolution of open lands and hence gave birth to bipedalism. From thereon, began the birth of closest Humankind ancestors of humans who walked on foot. From Dryopithecusto Australopithecus to Homo sapiens, modern humans evolved merely 40,000-10,000 years ago through the process of evolution, spanning along from 6 million years ago to 40,000 years ago.

2.7 KEY WORDS Bipedalism : the ability to walk upright. Fossil : remains or impressions of prehistoric plants, animals or humans. Human fossils are primarily found in the form of skeletons and teeth. Mutation : action or process of altering the structure of a gene. Paleoanthropologist : expert who studies the origins and predecessors of the present human species, using fossils and other remains.

2.8 ANSWERS TO CHECK YOUR PROGRESS EXERCISES Check Your Progress Exercise-1 1) See Sub-section 2.2 2) See Sub-section 2.3.1 3) See Sub-section 2.3.2 4) a) Exponentially, Arithmetic Rate b) Lamarck c) Natural Selection 5) Compare Sub-section 2.3.2 and 2.3.3 (see 2.3.3 carefully) Check Your Progress Exercise-2 1) See Section 2.4 and Sub-section 2.4.1 to 2.4.4 2) See Sub-section 2.4.1 3) See Sub-section 2.5.2 4) a) Lucy, Donald Johanson, Hadar in Ethiopia b) Wise Human c) Homo Erectus d) Olduvai Gorge in Tanzania, East Africa.

2.9 SUGGESTED READINGS Brown, P. 1992. ‘ in East Asia and Australasia’. Phil. Trans. R. Soc. Lond. B, 337(1280): 235-242. 48 Hall, B., & Strickberger, M. W. 2008. Strickberger’s Evolution. Jones & Bartlett Biological Learning. Evolution of Humans Krause, J., Fu, Q., Good, J. M., Viola, B., Shunkov, M. V., Derevianko, A. P., &Pääbo, S. 2010. ‘The complete mitochondrial DNA genome of an unknown hominin from southern Siberia’. Nature, 464(7290): 894. Rafferty, J. P. 2018. Gigantopithecus. Encyclopaedia Britannica. Raven, P. H., Johnson, G. B., Losos, J. B. & Singer, S. R. 2005. Biology Seventh Edition. New Delhi: Tata McGraw- Hill Publishing Company Limited. Reif, W. E., Junker, T., &Hoßfeld, U. 2000. ‘The synthetic theory of evolution: general problems and the German contribution to the synthesis’. Theory in Biosciences, 119(1): 41-91. Spencer, H. 1862. First Principles. McMaster University Archive for the History of Economic Thought. Smithsonian National Museum of Natural History. Accessed on August 28, 2017. https:/ /www.si.edu/ Stone, Linda, Lurquin, Paul F. and Cavalli-Sforza, L. Luca. 2006. Genes, Culture and Human Evolution: A Synthesis. New York: Wiley-Blackwell. PDF: How humans evolved. www.mhhe.com/biosci/genbio/raven6b/graphics/raven06b/other/raven06b_23.pdf https://www.britannica.com/animal/Gigantopithecus https://www.jstor.org/stable/pdf/4330635.pdf?refreqid=search%3A57645 ec65070a67f12177cb266930cc7 https://www.jstor.org/stable/pdf/192425.pdf?refreqid=search%3A1c2eb4888 7010d229bb6ab4511e283e5 https://www.jstor.org/stable/pdf/24931324.pdf?refreqid=search%3Aec37a33d 68c0038dbf95a1537f171fc0 https://www.jstor.org/stable/pdf/2742808.pdf?refreqid=search%3Ad44a9ef7270a9a d75f42b6c72cd2472a https://en.wikipedia.org/wiki/Human_evolution

2.10 INSTRUCTIONAL VIDEO RECOMMENDATIONS Origin of Humans https://www.youtube.com/watch?v=SUfujVWcj5I The Neanderthals: First Peoples of Europe https://www.youtube.com/watch?v=FbAptAnrwN8 New Human Ancestor Discovered: Homo naledi https://www.youtube.com/watch?v=oxgnlSbYLSc Ape to Man: Evolution Documentary https://www.youtube.com/watch?v=5sMqFivWTmk

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